The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
The micturition reflex is comprised of a plurality of interrelated neurological reflexes involved in urination. The function of the lower urinary tract includes maintenance of urinary continence and periodic expulsion of urine during voiding. The latter functions involve sympathetic, parasympathetic and somatic nerves. Continence is maintainable by urethral sphincter muscles, which preferably controllably contract the bladder urethra, acting as a valve. Discharge of urine is facilitated by sphincter relaxation. Urinary sphincters may also have an auxiliary function in maintenance of flow rate. Micturation also requires coordinated operation of the detrusor muscle, which locates inside the bladder wall. Impairment of one or more of the neurological reflexes associated with proper sphincter or detrusor action can result in inefficient or impaired bladder operation.
Cystometry is a diagnostic procedure for evaluating bladder function whereby an accurate picture of normal and abnormal micturition physiology is derived. Cystometric evaluation of micturition disturbances permits an orderly system of classification of neurogenic bladders. The procedure involves distension of the bladder by filling it with a gas or liquid through an inserted catheter. As fluid is inserted interiorly of the bladder, the relation between intravesical bladder pressure and inputted volume of fluid is graphically determined.
Sphincter electromyography is a diagnostic technique in which micturition electrical responses of the urinary sphincters are graphically displayed. Electromyography has been used in detecting lesions of the lower motor neurons and peripheral nerves and in diagnosing primary skeletal muscle disease. The sphincter response is sensed by utilization of externally contacting electrodes. Usually, electronic amplifying apparatus is provided to process the sphincter signals sensed by the electrodes such that the signal may be displayed; for example, on a strip chart recorder. The electromyogram (EMG) produced by the technique provides a useful graphical monitor of sphincter electrical activity, particularly where a patient is unable to control voiding.
U.S. Pat. No. 4,063,548 (Klatt et al.) describes a device for simultaneous cystometry and electromyography. The apparatus comprises a gas cystometry system for monitoring bladder detrusor reflexes and an electromyographic monitoring system which can be combined within a unitary enclosure. The cystometry system comprises a catheter for injecting fluid interiorly of the bladder and associated electronic circuitry for deriving interior bladder pressure. The electromyographic system comprises one or more electrodes for sensing sphincter electrical activity and electronic circuitry interconnected with the electrodes for amplifying sphincter electrical outputs. The electromyographic electrodes are operably mounted at the bladder-engaging end of a cystometric catheter. The device according to this publication does not, however, provide any facilities for sensing detrusor electrical activity.
U.S. Pat. No. 5,972,921 (Santti et al.) relates to a method for the treatment of detrusor urethral sphincter dyssynergia in men. The publication describes also a method for in vivo investigation of the urinary function based on an animal model of rats. The rats are anesthetized, provided with a pressure transducer connected to an infusion cannula inserted in the bladder, a flow probe inserted in the distal urethra and connected to a flow meter. The animals are infused with a solution into the bladder to induce micturition. The bladder pressure and urinary flow are registered as function of time. The rats are further provided with suction electrodes attached to the detrusor muscle, bladder neck and the external urethral sphincter (EUS, also called rhabdosphincter). The electrical activity of these muscles is thus registered simultaneously with the registering of the bladder pressure and the urinary flow.
The investigation method and device described in the cited patent would not be practical for routine diagnostic use on humans. The application of the suction electrodes on the muscles and the insertion of the infusion cannula through the bladder are invasive measures which would require anaesthesia of the patient and the assistance of a doctor.
So far, no publications have been found relating to non-invasive sensing of electrical activity of the detrusor muscle, with or without simultaneous recording of bladder pressure (transvesical cystometry) and flow rate. Simultaneous non-invasive sensing of detrusor muscle and external urethral sphincter electrical activities, optionally combined with sensing of bladder pressure, has not either been found in the art.